The instant invention relates to a low modulus joint sealant compatible with both portland cement and asphaltic concretes comprising a pourable two-component asphalt and urethane formulation offering excellent physical properties with respect to extendability, resiliency, bonding power and long wear life.
In roadway construction and repair, hot applied joint sealers have long been used. They are, however, criticized because of the inherent difficulties with keeping the material hot and moving equipment from one location to another. For example, heating equipment for the kettles, within which the hot sealants are melted, require an initial expense and then upkeep costs. One specific problem with kettle maintenance is that the thermometer oftentimes is rendered defective and the kettle may overheat. Time is also a factor inasmuch as there is a delay while waiting for the material to melt.
With most hot poured sealants the extendability, i.e. the ability to expand, is very low and therefore the force of pavement expansion and contraction causes the face of the pavement in contact with the sealant to tear away. Sufficient resilience in these prior sealants has been provided so that the sealer rejects foreign material from entering the crack, but but does not have adequate extendability to prevent the contraction and expansion of the pavement slab from cracking the slab between the joints.
Additional problems with previous attempts at both hot and cold applied sealers is that traffic must be re-routed for long periods due to the time required for the sealant to attain sufficient stability to resist tire tracking. Generally, the initial set-up time required to accept at least limited traffic has been from about six to twelve hours. In typical pavement joint maintenance procedures, traffic detours should be minimal. A substantially shortened set-up time is therefore desirable.
An asphalt/urethane combination has been suggested for a pourable cold applied sealer utilizing a polybutadiene liquid resin manufactured by ARCO Chemical Company under the trademark POLY BD.RTM.. This cold applied sealer has, however, a high percentage of urethane and provides a high modulus with low penetration. Such is suitable for portland cement concrete where adhesion can be maintained, but it is not particularly suitable with asphaltic concrete where adhesion is a critical concern to the industry.
Accordingly, it is a primary goal of the invention to provide a cold applied joint sealant having high extendability and the property of remaining soft at low temperatures.
It is an object of the invention to provide a cold applied joint sealant that is compatible with portland cement and asphaltic concretes.
It is another goal of the invention to provide a cold applied joint sealer that is self priming.
It is yet another objective of the invention to provide a joint sealant that reaches initial set in two hours or less in order to permit vehicles to be driven thereover.
It is a related objective of the invention to provide a cold applied joint sealant that has low urethane content, a low modulus and high penetration.
It is a concomitant goal of the invention to provide a cold applied joint sealant that comprises two constituents which are simply mixed in the field and ready for application to a crack or joint in less than ten minutes.
It is a concomitant goal of the invention to provide a two-component cold applied joint sealant wherein a first component comprises a urethane reactant in about 1% by weight of the final fomulation and is quickly mixable in the field with a second component comprising 99% of the formulation to form an asphalt/urethane sealer having a urethane content no greater than about 22%.